Dealing with Missing PV Module Performance Parameters

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Gloria Stevens
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Solmetric PV Analyzer Application Note January 2019, v2 Dealing with Missing PV Module Performance Parameters Introduction The Solmetric PV Analyzer compares the measured I-V curve with the an

1 Solmetric PV Analyzer Application Note January 2019, v2 Dealing with Missing PV Module Performance Parameters Introduction The Solmetric PV Analyzer compares the measured I-V curve with the an expected I-V curve shape derived from 17 module-specific PV module performance parameters along with the module azimuth and tilt, the current irradiance and temperature, and the date, time, and time zone provided by the PC that s running the PVA software. A complete list of the PV module performance parameters for an example PV module is shown in Appendix A. Some of the performance parameters are commonly found in PV module datasheets, but others are not. The PVA s PV module equipment database contains performance parameters for more than 50,000 PV modules. The performance parameters are obtained from PHOTON Databases in Germany. They cover most of the world s PV modules but, but some are missing because they are so new or the manufacturers never provided PHOTON with the data. Coverage of the 17 performance parameters is also very good, but in some cases one or more of the parameters is missing. When you select your PV module in the second screen of the New Project Wizard, a list of its performance parameters appears, as shown in Figure 1. Scroll downward to see the rest of the 17 parameter values. Figure 1 The PV module selection screen in the PVA software. 1

The questions this application note addresses include: How do I update my equipment database? How do I deal with missing PV module performance parameters? What if a PV module is missing?

2 The questions this application note addresses include: How do I update my equipment database? How do I deal with missing PV module performance parameters? What if a PV module is missing? How do I update my equipment database? If you have an active internet connection when you launch your PVA software, the software accesses Solmetric to see if an update to the PV module database is available. If so, it asks if you would like to install it. Click Yes, and the update will complete in approximately 1 minute. You do not need to restart your software, and there is no fee for the update. You may also be asked if you want to update the inverter equipment database. You may want to skip this, because the inverter parameters have no effect on either the I-V curve measurement or the predicted I-V curve. When you advance to the next Wizard screen to create your array tree, you can just leave the inverter undefined. How do I deal with missing PV module performance parameters? If a performance parameter value is missing, the number box is outlined in red as shown in Figure 2. Figure 2 Missing values in a set of performance parameters. 2

3 In some cases of missing parameter values, the PVA software automatically inserts an estimated default parameter value. This is done only in cases where the values is fairly generic and the impact on PV performance modeling is relatively slight. A notation appears beside the parameter value s number box, indicating that it is a default value. You can go with that parameter value or opt to research and enter the missing value. If the missing parameter is critical for satisfactory performance modeling, the Wizard will not advance to the next screen without a value in that box. Let s assume you are dealing with a critical missing parameter. Look for the missing parameter in your PV module datasheet. If the datasheet provides the value, click the pencil icon for that parameter and enter that value. Be sure the units (volts, amps, etc.) match what the software expects. Absolute temperature values like NOCT must be entered in units of degrees Centigrade. However, for the temperature coefficients, you can enter values expressed in degrees C or degrees K. (the Kelvin and Centigrade temperature scales have very different absolute temperature references, a degree of temperature change in the Centigrade scale is identical to a degree of temperature change in the Kelvin scale). If the missing parameter is not in the datasheet, check the California PV Module List at If you don t find the parameter in the California list, call the PV module manufacturer for Technical Support. Solmetric does not have these missing parameter values! If you did not enter a missing parameter but simply corrected a parameter value, a notation will appear to the right of the number box showing the parameter value that was in the box prior to your change. Click on that link to revert the parameter back to that value. See Figure 3. Figure 3 Wizard screen after entering a missing parameter or editing an existing parameter. 3

When you make any changes to the performance parameter list, additional controls at the bottom of the screen become active. Click the Rename button and the form shown in Figure 4 appears.

4 When you make any changes to the performance parameter list, additional controls at the bottom of the screen become active. Click the Rename button and the form shown in Figure 4 appears. In the Model entry box, edit the Model Name as needed to draw attention to the fact that you edited or added a parameter value. Then click OK. Figure 4 Edit the PV module s Model Name after editing or adding a performance parameter. Once you have created a Custom Module in this way, the Wizard screen automatically selects this module. If you need to use that Custom Module in a future project, just click the Custom radio button in the Wizard, as shown in Figure 5, to bring up a list of your custom modules, and select your module. 4

5 Figure 5 Recalling a Custom Module In some cases it is possible to estimate the value of a missing parameter. For example, some PV module datasheets do not list the temperature coefficient of Nominal Power. If the temperature coefficient of Imp is very small relative to the temperature coefficient of Vmp, you can reuse the value of the Vmp coefficient for Nominal Power. What if a PV module is missing? If you have updated your equipment databases and your PV module is still not included, you will need to create a custom PV module for it in the Wizard, using parameter values you obtain from PV module datasheets or the manufacturer s technical support or applications engineering department. In some cases, you can save time by selecting a similar PV module from the equipment database and editing its parameter values. For example, if you are using the 320W module that you know is a new addition to a particular family of PV modules, find the family datasheet and notice how the parameters change across the family. For example, notice how the temperature coefficient of Voc changes across a family of 300W, 305W, 310W, and 315W modules. If the value is consistent, you can use that same Voc temperature coefficient value in your custom module. Many of the performance parameters are not obtainable from datasheets, and you will need to call your module maker s technical support or applications engineering departments. Solmetric does not have these missing parameter values! If the equipment database doesn t have similar PV module for you to edit, click the New Custom button to create a fresh custom module. The Create New Custom Module form appears, as shown in 5

6 Figure 5. Enter the name of the manufacturer and the model, and follow the model name with a word or two of explanation to distinguish it. Figure 5 Create a New Custom Module. Hit the New Custom button to get started. 6

7 Appendix A PV Module Parameters January 2019, v2 Following is an example of an unedited set of PV module parameters. The module is a SunPower SPR- 445NX-WHT-D. This is a high-efficiency module. 7

ShineNet. Growatt Version Date Notes New. ShineNet V1.0

ShineNet. Growatt Version Date Notes New. ShineNet V1.0 ShineNet Growatt 1.0 2012-09-25 Version Date Notes 1.0.0.2 2012-09-25 New Table of Contents 1. Introduction...3 2. Install and Uninstall...4 2.1 System requirements...4 2.2 Install software...4 2.3 Uninstall